Ubiquitous Computing: Trends and History - College of Computing
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Ubiquitous Computing: Trends and History
Lecture 2
CSI 660, William A. Maniatty, Dept. of Computer Science, University at Albany 1
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Introduction
Review: What is Ubiquitous Computing?
• Immerses computers in a real environment
• Sensors support interact with and control the environment.
• Limited power supply, storage, memory and bandwidth.
• Operate unattended (much like embedded systems).
• Devices are mobile/wireless.
• May reside on a person (wearable computing).
• Have special peripherals.
• Contrast this with virtual reality which immerses humans in a computer generated arti�cialenvironment.
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Historical Origins and Trends
Computers are becoming smaller and cheaper over time
• Originally few computers many operators
. Machines Expensive and Large
. People (relatively) cheap
• Trend toward more computers per person
. Users may not be tech savvy
. Even tech savvy users have limited time
. Minimal intervention is required
People don't want to be separated from their data
• But spying on users upsets them
• And can violate laws - security is important
• Mobility and wireless access are critical.
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Some Popular Views
Many visions were popularized in the press
• First to work on it, although other visionaries preceded him
• Entertainment Industry (Ian Fleming, Gene Rodenberry)
• Vanaver Bush's seminal article [1] As We Might Think predicted the WWW and UbiquitousComputing in 1945!
• Vernor Vinge (retired Computer Science Professor and Science �ction writer) has interestingubiquitous computing visions.
• Movies: The Terminator, numerous Philip K. Dick books and screen plays (Blade Runner,Total Recall, Minority Report).
Has been popular in the research community for over a decade
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A historical view from 1993
Weiser [4] is credited with popularizing ubiquitous Computing
• Work began at Xerox PARC in 1988
• Ubiquitous Computing is NOT:
. virtual reality � real world provides input, not computers!
. A PDA or PC � Called an intimate compute, takes your attention to get it to do thework
• Ubiquitous Computing
. Supports a world of fully connected devices
. Ensures information is accessible everywhere
. Provides an intuitive, nonintrusive interface, feels like you are doing it
• Challenges Include:
. Wireless bandwidth � high speed and highly multiplexed
. Handling mobility
. User Interface (window systems)
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Computational Issues Back in 1993
Weiser [5] started work in 1988 and reported in 1993
• He didn't want an intimate computer
• Initially Virtual Reality (VR) seemed to have similar design approaches
. VR gets the computer out of the way (supports intuitive interaction)
. But VR has serious problems
. Making su�ciently realistic simulations is expensive (and probably will be fordecades)
. VR locks users away from reality
• Multimedia is di�erent as it seeks to attract your attention
• Di�erent from Assistants (e.g. PDA or Intelligent Agents) which work for you
. Imagine a heavy rock being lifted by an assistant
. Imagine being able to lift the rock yourself (e�ortlessly)
• Informal Goal: Computing for every day life
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Weiser's Design Goals
Used the construction of everyday things
Focused on physical a�ordances
• Wall Sized Interactive Surface
• Notepad
• Tiny computer (e.g. light switch sized)
Developed Hardware Prototypes:
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Weiser's Design Approach
Liveboard - digital white-board
Tab - Tiny information portal
• Power is a major issue, cannot always change batteries
• Batteries large and heavy relative to other components
• Used COTS Intel 8051 microcontroller
Pad - Notebook based device
• Originally tethered Sun SBus, later untethered
• Always ran XWindows
• Used Pen interface
• Built in house to satisfy design goals:
. Control of balance in prioritizing design criteria
. Ability to ensure inclusion of design features
. Ease of expansion and modi�cation
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Computer Science Time Capsule 1993
Desktop Processor Architecture of the day
• Intel Pentium Released in 1993, 3.1 million transistors.
• Blazing Speeds of 60 and 66 MHz, about 100 Mips
• Memory Speeds were about 66 MHz
• RISC architectures were faster (but were mostly UNIX based).
• Windows 3.1 Popular (some people ran MS DOS still).
• Windows NT was brand spanking new!
• Linux was 2 years old.
• WWW was just beginning to be noticed, internet mostly in labs
• Wireless almost exclusively meant cell phone back then
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Weiser's Computational Issues
Computer Science Issues
• Reduce Power Consumption
Power = Gate Capacitance× Supply Voltage× Clock Frequency (1)
. Chips in 1993 didn't have power saver modes
. Most chips had failures when underpowered
• Wireless data protocols were not widely deployed, still in the lab
• Pens for very large displays
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Weiser's Wireless Networking Issues 1 of 2
Media Access Control (MAC) protocols
• Supports multiplexing broadcast media
• Chose MACA - avoids undetected collisions which garble signals.
. MACA uses time division multiplexing
. All nodes must have the same transmission radius
. Nodes don't transmit when the channel is busy.
. Message sizes are advertised (to let listeners know how long they need to wait).
. When a node wants to transmit it sends a Request to Send N Bytes (RTS).
. When the receiver detects the channel is clear it sends a Clear to Send (CTS) N Bytes
. If a collision occurs all stations should back o� the same amount.
Physical layer was challenging
• FCC regulations and technology drove them to 900 MHz bandwidth
• 1990 technology was not up to spread spectrum
• But my o�ce phone used to have it (before it failed)
• Went with low power frequency shift keying (FM) approach
• Low power reduces media contention and avoids FCC regulations
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Weiser's Wireless Networking Issues 2 of 2
Wide Bandwidth Range
• MACA needed fairness guarantees
• and di�erentiated QoS
• Added a Not Clear to Send (NCTS) packet for bandwidth reservation by base stations.
Real Time Multimedia Protocols
• QoS needed for streaming multimedia
• May need higher layer
Packet Routing
• Need base station load balancing
• IP not designed to support mobility
. However, it is dominant
. OSI ISO 8473 Connectionless Network Protocl (CLNP) has some mobility support, butis less popular
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Weiser's Interaction Substrates
Interaction Substrate is what we call the UI Toolkit
• Windowed Mouse Point and click (WiMP) are still dominant
• XWindows designed for networked use
. Speci�es policy not appearance
. Attempts to be device independent (e.g. units of length measures used are not)
• Display areas vary between physical devices
. Pads often have tiny interaction areas
. Liveboards have huge interaction areas
• Input devices depend on size
. Pads need pens, since keyboards are too big.
. Pens needed special script since general handwriting mechanism is too hard
• Added support for migrating windows in X.
• Proposed support for low bandwidth network connections (vary protocol according to band-width).
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Weiser's Applications
Applications
• Locating People
. Data acquired from:
. Log ins to workstations/terminals
. An Active badge system (smart badges?)
. Useful for
. Automatic call forwarding
. Shared Drawing Tools
. An Active badge system (smart badges?)
• Shared Drawing
. Data Representation
. Object (vector) based
. Bit mapped
. UI Issues
. How to handle multiple cursors?
. Use gestures or not?
. Use an ink based or character recognition model of pen input?
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Impending Application Concerns
Characteristics of future Ubicomp Applications
• Smart environment (hiding computing in walls/infrastructure)
• Virtual Communities
• Information �ltering (streaming data management)
Weiser expects security concerns
• Preserve privacy by aggregating information
• Nontechnical issues are important
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Computational Issues raised by Weiser
Cache Coherence Problem
• Classical distributed computing problem
• Consider multiprocessor machine with a single address space
• If 2 processors have the same location cached, how do they make sure they see the same value?
How close to the theoretical optimum can on-line cache coherence algo-rithms get in practice?
Especially if pages can be compressed.
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Mann's De�nition of Wearable Computing (1998)
Steve Mann [2] states a wearable computer is:
• Subsumed into the personal space of the user
• Controlled by the user and
• Always on and always accessible.
Modes of Operation (how does interaction work?)
• Constancy: The computer runs continuously, and is �always ready�
• Augmentation: The computer helps the user to do other stu� by enhancing his mind or senses
• Mediation: The computer �lters information relayed to the user and regulates what informationthe user wishes to disclose
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Mann's 6 Attributes of Wearable Computing
The Six Attributes of Wearcomp
• Unmonopolizing of the user's attention.
• Unrestrictive to the user: ambulatory, mobile, roving,
• Observable by the user, can alert you when necessary.
• Controllable by the user: responsive.
• Attentive to the environment: Environmentally aware.
• Communicative to others.
InputsDirect
FilteredInputs Attentive
User
Wearcomp
Unmonopolizing User’s Response
WearcompResponse
ControllableObservable
Unrestrictive
Communicative
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Aspects of Wearable Computing
Aspects of wearable computing and personal empowerment
• Photographic memory: Perfect recall of collected information.
• Shared memory: Individuals may share their recorded experiences.
• Connected collective humanistic intelligence, facilitate collaboration
• Personal safety: The wearcomp can allow for distributed protection from danger.
• Tetherless operation: Wearable computing a�ords and requires mobility.
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Satyanarayanan's Approach (2001)
Satyanarayanan [3] (Satya for short) discussed current issues:
• Calls Ubicomp Pervasive Computing
• Several Example Groups:
. Project Aura at CMU
. Edeavour at UBC
. Industrial AT&T research Cambridge U.K. (Stajano?)
. IBM TJ Watson (Westchester County, NY)
• Contrasts with Prior Art/Related Fields
. Distributed Systems (tethered)
. Mobile Computing (untethered)
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Distributed Systems and Mobile Computing
Satya characterizes distributed systems as having (1980's research):
• Remote communication � protocol layering (e.g. rpc's, timeouts, 2 phase commit).
• Fault Tolerance - Atomic/nested/distributed transactions, 2 phase commit.
• High Availability � Optimistic/Pessimistic replica control, mirrored execution and Optimisticrecovery
• Remote Information Access - Caching, Code Migration, distributed �le systems and distributeddatabases.
• Security - Encryption for mutual authentication and privacy.
Mobile Computing (1990's research) adds :
• Mobile Networking - Mobile IP, Ad Hoc protocols, Wireless TCP
• Mobile Information Access - disconnected operation, bandwidth adaptive �le access, selectivecontrol for data consistency.
• Support for adaptive applications - Adaptive Resource Management, Transcoding by Proxies
• System Energy Management - Energy aware adaptation, Architectural Support
• Location Sensitivity - Location sensing, and location aware system behavior.
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How is Pervasive Computing Di�erent?
Smart Spaces
• Use Computing Infrastructure embedded in a building to assist the user.
Invisibility
• The computer should not distract the user
Localized Scalability
• Adding Ubicomps to a smart space should not overtax the infrastructure
Masking Uneven Conditioning
• In spite of variable smart space deployments, a user should have a consistent experience
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Can We Improve Pervasive Computing
Proactive handling of user needs
• Ability to predict system behavior given conditions e.g. Wireless congestion is a low level
• Recognize constraints - want to send e-mail before departing �ight
. Wait for slow e-mail could cause missed �ight
. Leave for �ight prevents e-mail
. Realize that constraint is spatially localized
• Clever use of smart spaces may �nd alternatives
. e.g. Suggest uncongested regions of airport
Self-Tuning - adjust behavior to circumstances
• Sense user intent, predict likely user needs
• Code and Data Migration
. Put the access where the user is
. Alert smart space infrastructure to prepare for user's arrival
• Alert user to potential constraint violations
. Warn user before transmitting con�dential data
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Drilling Down
Ubicomp provides sort of virtual immersion
• Like VR
• But it goes with the user
Ubicomp devices worn by the user are called clients.
• Not in the client-server sense
We need a layer above the applications (Prism)
• To coordinate the constraints of applications
• To sense user intent
Remote execution support via Spectra
Nomadic �le access via Coda
Resource monitoring and adaptation using Odyssey/Chroma
Linux Kernel
Intelligent Networking
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User Intent
Guessing User intent is hard
• Hence modern systems don't do this well!
• Why? Generic applications lack enough information
. e.g. Viewing Streaming Video and network bandwidth suddenly drops
. Should the application:
. Wait for less contention
. Reduce display �delity
. Tell the user that the service is unavailable
• Bad User Intent systems are intrusive
. Do you really want Microsoft's �Clippy� to help?
• Research Opportunities!
. Can user intent be inferred, or does the user need to explicitly signal intent?
. How can user intent be represented?
. How can we measure accuracy in measuring user intent?
. Will the attempt to obtain intent cause a burden to the user exceeding the bene�t?
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Cyber Foraging
Cyber Foraging does nomadic resource discovery
• Cheap computing means �waste� is not so bad
• Is Communication or Computation cheaper?
. Computation Cheaper � Owner Computes
. Communication Cheaper � Find a surrogate
. How to decide? Must know bandwidth, size of inputs, outputs and code to migrate tobe sure.
• More Research Opportunities!
. How can a device best �nd surrogates?
. How can trust be established with surrogates?
. How is load balancing done between surrogates?
. How much advance notice does the surrogate need to avoid excessive delay?
. What are the implications for scalability?
. What system support is needed to make surrogate use minimally intrusive?
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Additional Research Areas
Adaptation Strategies � Adjust to variable constraints
• Is reservation based QoS approach correct?
• Is it feasible to use corrective actions to support adaptation?
High Level Energy Management
• Can user intent generate meaningful hints for energy management?
• Can smart spaces and surrogates reduce demand on a mobile device?
Client Thickness � Trade-o� between functionality and complexity
Context Awareness � Needed for Minimizing Intrusiveness
• Context is users state and his surroundings - how to represent this?
• What are the merits of di�erent location sensing technologies?
Balancing Proactivity and Transparency
Privacy and Trust
Impact on Layering
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Brief Note on Timestamp Ordered Protocols and PDES
In lecture I mentioned brie�y about Parallel Discrete Event Simulation(PDES).
Each Simulation Entity has a discrete state
Entities represented via logical processors (LP)
LPs communicate via time stamped messages
LPs advance simulation state (and time) by processing messages.
Why is PDES Hard?
• Local Causality Constraint - Must ensure that each LP processes (interfering) messages innondecreasing time stamp order.
• Some processors may be slower, and late messages (stragglers) are a problem.
• For e�ciency, we don't want to restrict order of processing.
Flavors of protocols
• Optimistic - Uses Speculative Execution, with rollback or reverse computation.
• Conservative - Only processes messages when it is safe.
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Challenges In PDES
Empty
Non Empty
An Example of Deadlock
12
10
8 2521
22
α
β γ
Conservative Protocols are Susceptible to deadlock
Optimistic protocols not much easier
• Tend to have cascading rollbacks
• Tend to use a lot of memory for checkpoints
• Need to compute Global Virtual Time (time of last correctly processed event).
• Hard to know when checkpointed data is safe to discard
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Bibliography
References
[1] Vanaver Bush. As we may think. The Atlantic Monthly, July 1945. On line athttp://www.csi.uottawa.ca/ dduchier/misc/vbush/awmt.html.
[2] S. Mann. De�nition of "wearable computer". On line athttp://wearcomp.org/wearcompdef.html, 1998. From Mann's Keynote Addressentitled "WEARABLE COMPUTING as means for PERSONAL EMPOWER-MENT" presented at the 1998 International Conference on Wearable ComputingICWC-98, Fairfax VA, May 1998.
[3] M. Satyanarayanan. Pervasive computing: Vision and challenges. IEEE PersonalCommunications, pages 10�17, August 2001.
[4] Mark Weiser. Hot topics: Ubiquitous computing. IEEE Computer, October 1993.On line athttp://www.ubiq.com/hypertext/weiser/UbiCompHotTopics.html.
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[5] Mark Weiser. Some computer science issues in ubiquitous computing. CACM,36(7):74�83, July 1993.
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